Cross-linked polyamide-imine polymer for papermaking

ABSTRACT

Cross-linked reaction products obtained by (a) reacting 1 mole of a dicarboxylic acid such as adipic acid with 0.8 to 1.5 moles of a polyalkylene-polyamine such as diethylenetriamine and/or up to 0.4 mole of an omega -aminocarboxylic acid such as W-aminocaproic acid or a lactam thereof, (b) reacting the reaction product of step (a) with 1 to 30 moles of a 1,2-alkylenimine compound such as ethyleneimine per mole of basic nitrogen in the reaction product of step (a) in the presence of a small amount of acid or alkylating agent such as sulfuric acid as catalyst and (c) cross-linking the reaction product of step (b) with 1 to 20 parts of a bifunctional compound such as epichlorohydrin per 100 parts of reaction product. Twenty-five percent solutions of the new products have a viscosity of from 300 to 4,000 centipoises at 25* C.

1Jited States Patent Endres et al.

[54] CROSS-LINKED POLYAMIDE-IMHNE POLYMER FOR PAPERMAKING [72]Inventors: Horst Endres; Rolf Fikentscher; Walter Maui-er; Emil Schart;Uwe Soenksen, all of Ludwigshafen, Germany [73] 'Assignee:

[21] Appl. No.: 864,216

[30] Foreign Application Priority Data I Oct. 11, 1968 Germany 18 02435.6

[52] US. Cl. ..l62/ 164, 260/2 EN, 260/78 SC [51] Int. Cl. ..D21h 3/36[58]v FieldoiSearch ..162/164; 260/78 SC,2EN, 561 A [56] ReferencesCited UNITED STATES PATENTS 3,224,986 12/1965 Butler ..260/78 SCFeb.]15,1972

3,250,664 5/1966 Conte 162/ 164 3,294,723 12/1966 Goldstein 3,520,7747/1970 Roth 1 62/164 [5 7] ABSTRACT Cross-linked reaction productsobtained by (a) reacting 1 mole of a dicarboxylic acid such as adipicacid with 0.8 to 1.5 moles of a polyalkylene-polyamine such asdiethylenetriamine and/0r up to 0.4 mole of an cp-arninocarboxylic acidsuch as W-amino-caproic acid or a lactam thereof, (b) reacting thereaction product of step (a) with 1 to 30 moles of a 1,2-alkyleniminecompound such as ethyleneimine per mole of basic nitrogen in thereaction product of step (a) in the presence of a small amount of acidor alkylating agent such as sulfuric acid as catalyst and (c)cross-linking the reaction product of step (b) with 1 to 20 parts of abifunctional compound such as epichlorohydrin per 100 parts of reactionproduct. Twenty-five percent solutions of the new products have aviscosity of from 300 to 4,000 centipoises at 25 15 Claims, No DrawingsCROSS-LINKED POLYAMlDlE-HMINE POLYMER FOR PAPERMAKHNG The inventionrelates to the production of new reaction products of polyamidoamineswith 1.2-alky1enimines and bifunctional cross-linkers which are valuableauxiliaries for the manufacture of paper.

It is known that polyethylenimine may be used in papermaking as aretention agent for fillers and fibers, as an agent for ac celeratingdewatering in the formation of the sheets and as a flocculant in therecovery of fibrous material. Furthermore it is known from U.S. Pat. No.2,849,411 and from British Pat. No. 1,156,516 that an auxiliary forpapermaking is obtained by reaction of diamines and polyamines withepichlorohydrin. It is moreover known that paper auxiliaries can be madeby cross-linking polyamidoamines for example with epichlorohydrin. Thesegroups of products have the disadvantage that each exhibits an optimumeffect in the manufacture of paper within a limited pH range.

Cross-linked polyamines have their optimum effect in the neutral pHrange, cross-linked polyamidoamines in the acid pH range. However, inpapermaking more or less rapid changes of manufacturing conditions fromacid to neutral usually occur as a result of changes in the nature ofthe raw material.

The obvious course is to use a mixture of the two products.

It has been found however that the effect in the acid and neutral rangescorresponds only proportionately to the components in the mixture.

We have now found that, surprisingly, effective auxiliaries for thepaper industry based on basic polyamidoamines which are particularlysuitable as flocculants, retention agents and dewatering agents inneutral and acid media are obtained by grafting onto the basicpolyamidoamine from 1 to 30 moles per mole of basic nitrogen in thepolyamidoamine of a 1,2-alkylenimine compound having the generalformula:

in which R and/r R denotes a hydrogen atom or a lower alkyl radicalhaving one to three carbon atoms at a temperature of from 25 to 110 C.in the presence of 0.005 to 1.0 equivalent of acid or alkylating agentper mole of basic nitrogen in the polyamidoamine and cross-linking theresultant resin in aqueous solution with from 1 to 20 parts ofabifunctional compound for each 100 parts of 100 percent resin to form ahigh-molecular weight resin until a 25 percent by weight aqueoussolution of the resin has a viscosity of more than 300 centipoises at 25C.

The basic polyamidoamines used as starting material for the grafting areknown compounds which can be obtained by condensation of dicarboxylicacids such as succinic acid, maleic acid, adipic acid and/orterephthalic acid with polyalkylenepolyamines such asdiethylenetriamine, triethylenetetramine, dipropylenetriamine ortripropylenetetramine. The ratio of dicarboxylic acid topolyalkylenepolyamine is from 1 0.8 to l 1.5 moles, preferably from 10.9 to l 1.2 moles. Condensation is carried out by a conventional methodat elevated temperature, the water formed in the reaction advantageouslybeing distilled off.

The water-soluble basic polyamidoamines obtained have viscosities in 50percent by weight aqueous solution of more than 100, preferably from 150to 2,000 centipoises (at 25 C.) and a content of basic nitrogen of from2.8 to 14 percent, preferably from 4.2 to 8.4 percent, by weight withreference to the 100 percent resin. Viscosity is determined in theHoeppler viscometer by the falling-ball method.

Diamines such as ethylenediamine, propylenediamine orhexamethylenediamine and/or aminocarboxylic acids or their lactams suchas caprolactam may additionally be condensed with these polyamidoamines.

The polyamidoamines serving as starting materials thus contain thefollowing structural units:

0 0 If H o H il 1' l CACNB-N-CA.\'

(branched) F/ v L\CH2) N] (CH): l t; A

(crossllnked) 1,2-polyalkylenepolyamine side chains can be grafted ontothese basic polyamidoamines by reaction with 1,2-alkylenimines.1,2-alkylenimines such as 1,2-propylenimines and above all ethylenimineare suitable for this purpose. For grafting, 1 to 20 moles, preferably 2to 15 moles, of 1,2-alkylenimine (per mole of basic nitrogen in thepolyamidoamine) is slowly added to a solution of the polyamidoamine inthe presence of 0.005 to 1.0 equivalent (per mole of basic nitrogen inthe polyamidoamine) of an acid catalyst at a temperature of from 25 to 110, preferably from 40 to 100 C. It is advantageous to carry out thereaction in 30 to percent by weight aqueous solution, preferably in 40to 90 percent by weight aqueous solution, with reference to thepolyamidoamine. Grafting may also be carried out in an organic medium.Catalysts known from the polymerization of ethylenimine, such as acidsor alkylating agents, may be used as catalysts for grafting. The acidsinclude those proton acids which are able to act as proton donors underthe reaction conditions and compounds which have an electron gap at thecentral atom and consequently can add on to the free electron pair ofthe basic nitrogen atom in the ethylenimine. The latter compounds areknown as Lewis acids. Suitable acids for grafting include sulfuric acid,phosphoric acid, perchloric acid, hydrochloric acid, boronfluoridehydrate, chloroacetic acid, organic sulfonic acids, zinc chloride,aluminum chloride, dimethyl sulfate, 1,2-dichloroethane and/ortoluenesulfonic esters. Sulfuric acid and above all p-toluenesulfonicacid have proved to be particularly suitable for grafting.

Owing to the high proportion of basic NH and NH, groups available in thepolyamidoamines, the 1,2-alkylenimine mainly reacts with thepolyamidoamine with the formation of aminoethyl or polyaminoethyl sidechains. Even when small amounts of low-molecular weightpolyalkylenimines are formed, these react in the course of the reactionwith the basic polyamidoamine (because an excess of polyamidoamine andgrafted product is always present):

(R denoting the radical of the polyamidoamine or of the grated-onpolyalkylenimine; R denoting a hydrogen atom or having the same meaningas R) The grafted products are sometimes referred to as grafted resinsor l,2-alkylenimine-polyamidoamine reaction products.

The resin is cross-linked into water-soluble viscous resin of highermolecular weight in aqueous solution by means of bifunctional compoundsknown as cross-linkers. It is advantageous to carry out thecross-linking in 10 to 40 percent, preferably 15 to 30 percent, byweight aqueous solution with reference to the grafted polyamidoamine attemperatures of from 40 to 100 C. Suitable cross-linkers arebifunctional compounds which react with amines in an aqueous medium.Examples of suitable compounds are dichlorobutene, dichlorobutane ordiisocyanate derivatives. Epichlorohydrin, acrylic esters andpolyepoxides have proved to be particularly suitable crosslinkers.Examples of suitable polyepoxides are reaction products ofpentaerythritol and/or glycerol with epichlorohydrin. A cross-linkercontaining 0.5 to 0.8 equivalent of epoxy groups per 100 g. ofcrsslinker and to percent of organically combined chlorine isparticularly effective. Since the polyepoxides have little or nosolubility in water, they are advantageously used in the form ofsolutions in water-soluble alcohols, e.g., methanol, ethanol andpropanol.

Products which are useful in papermaking are obtained by cross-linkingthe grafted products into high-molecular weight resins to such an extentthat their 25 percent by weight aqueous solution has a viscosity of morethan 300, preferably more than 500, centipoises at 25 C. The viscosityis determined by the falling-ball method in a Hoeppler viscometer. Theeffectiveness of the products increases as the degree of cross-linkingincreased, i.e., as the viscosity increases. Products having very highviscosity, however, have a strong tendency to gel. In production andprocessing difficulties arise because of the viscosity rising rapidlywith increasing cross-linking, so that there is an upper limit tocross-linking. Products may be processed well up to about 4,000centipoises in to percent by weight solution at 25 C., equivalent to aspecific viscosity of 0.8 to 2 (measured as a 1 percent by weight resinsolution in 2 percent by weight aqueous common salt solution at 25 C Theamount of bifunctional compound required for crosslinking naturallydepends on the constitution of the 1,2-alkyleniminc-polyamidoaminereaction product. On the other hand, even with the same starting resin,for example in crosslinking with epichlorohydrin, the higher thereaction temperature and the higher the water content of the resinsolution, the more epichlorohydrin is required for the production ofasolution having a given viscosity (because of hydrolysis of thecross-linker which always occurs at the same time). Generally from 1 to20 parts, preferably from 2 to 10 parts, of hifunctional cross-linker isrequired for each 100 parts of 100 percent by weight resin. Productswhich have been prepared by cross-linking with 2 to 6 parts ofcross-linker, such as epichlorohydrin and polyepoxides, are particularlyeffective.

Cross-linking may be carried out by adding the amount of cross-linkerrequired for the degree of cross-linking desired either all at once orin portions. The course of the cross-linking is watched by observing theincrease in the viscosity of the solution. Adding the cross-linker inportions is preferred because the cross-linking reaction can becontrolled better and the risk of the reaction mixture gelling is muchless. Furthermore overdosage can be avoided in this way and a specificviscosity can easily be set up.

Cross-linking may also be carried out by adding the crosslinker to thesolution of the grafted product at room temperature, heating thereaction mixture to the desired temperature and completing thecross-linking at this temperature until the viscosity ofthe solution nolonger increases.

The cross-linked l,2-alkylenimine-polyamidoamine reaction products arestrongly basic because of the amino groups which they contain. Theeffectiveness of the cross-linked reaction products as dewatering,flocculating and retention agents is however not affected byneutralization of the resin solutions with acids.

The agents according to the invention in the overwhelming majority ofcases constitute an advance in the art since they are universallyapplicable. Furthermore, as compared with products based on cross-linkedpolyamidoamines and crosslinked 1,2-polyalkylenamines, they have aclearly better effect as regards retention of filler and dye,acceleration of dewatering and flocculation or flotation in the recoveryof material during paper manufacture. It is possible to use theseproducts in every pH range occurring in papermaking. The products of theinvention may be used in the production of papers of all types, sizedand unsized glazed boards, and in the presence or absence of aluminumsulfate.

The invention is illustrated by the following Examples, in which partsand percentages are by weight.

EXAMPLE 1 a. 1,000 parts ofdiethylenetriamine in a heatable vesselprovided with a stirrer, thermometer and descending condenser has 500parts of water and 1,450 parts of adipic acid added to it. As soon asthe adipic acid has dissolved, the whole is heated under nitrogen to abottoms temperature of 190 C. within 3 hours and the water is thusdistilled off. After condensing for 4 hours at 190 C., the melt iscooled at a subatmospheric pres sure of 10 mm. Hg. to 150 to 140 C. and2,000 parts of water is added to the highly viscous polyamidoamine at130 C. The aqueous solution obtained is characterized by the followingdata:

Solids content: 50.9 percent (determined by drying 0.5 g. of resin for 2hours at 120 C. in a drying cabinet) Viscosity: 1,361 centipoises at 25C. (determined by the falling-ball method in a Hoeppler viscometer) Acidnumber: 3.74 (with reference to 100 percent product) Basic nitrogen: 6.2percent (with reference to 100 percent product) Specific viscosity: 0.16(measured as a 1 percent resin SOlU- tion in 2 percent aqueous commonsalt solution at 25 C.)

b. 10 parts of p-toluenesulfonic acid is added to 491 parts of the resinsolution (la) and the whole is heated to 65 C. 244 parts of ethylenimineis dripped in within 3 hours. The temperature of the reaction solutionrises during the addition of ethylenimine. The temperature is kept atfrom to C. during grafting. When all the ethylenimine has been added,the whole is kept at 80 C. for another 2 hours and then the solution isdiluted with 980 parts of water.

c. Epichlorohydrin is slowly metered within 6 hours at 60 C. into thesolution (lb) and the increase in viscosity is observed. After 12.4parts of epichlorohydrin has been added (9.4 parts within the first 2hours and 3 parts within the remaining time) the resin begins to gel.The highly viscous solution is diluted with 550 parts of water and thesolution is kept at 60 C. for another hour. The solution of the endproduct as a density of 1.020 g./cm., a viscosity (determined as above)of centipoises in 15 percent solution at 25 C. and a specific viscosity(determined as above) of 0.95.

The following Tables give a comparison of the papertechnologicalproperties of the end product with those of a cross-linkedpolyethylenimine (PEI) which has been prepared according to British Pat.No. 1,156,516.

Measuring methods:

Acceleration of Dewatering This is characterized by the increase infreeness in SR (degrees Schopper-Riegler) according to the method ofInstruction Sheet 107 of the Verein der Zellstoffund Papierchemiker undlngenieure (Association of cellulose and paper chemists and engineers).

Filler Retention This is characterized by the ash content of sheets ofpaper, prepared on the Rapid-Kothen apparatus according to InstructionSheet 108 of the Verein der Zellstoffund Papierchemiker und Ingenieure.

80% of bleached sulfitc cellulose 35 SR 20% of china clay. 0.24g./liter.

test paper material:

TABLE la ACCELERATION OF DEWATERING (measured as increase in freeness inSR) Pulp: Newsprint, beaten free from specks in an Ultraturraxapparatus.

FILLER RETENTION: percent of ash in paper; addition 0.015 percent of 100percent resin with reference to cellulose and filler.

pH value of fiber suspension 6' 4.5 addition of alum with reference tocellulose plus filler 0.5% 3.5% O-value 6.4 6.5 cross-linked PEI(according ash to British Pat. No. 1,156,516) 8.1 6.5 in pa er Example10: 8.8 8.1

EXAMPLE 2 a. 530 parts of water, 667 parts of a mixture of 91.5 percentof diethylenetriamine and 8.5 percent of triethylenetetramine and 925parts of adipic acid are heated under a nitrogen atmosphere within 3.5hours to 160 C. and kept at this temperature for 5 hours so that thewater distils off. The polyamidoamine formed has 1,400 parts of wateradded to it at 130 C. (solids content 48.3 percent). The resin solutionobtained has a density of 1.095 g./cm. and a viscosity (determined asabove) of 320 centipoises at C.; the content of basic nitrogen is 7.0percent with reference to the 100 percent product.

b. 15.5 parts of concentrated sulfuric acid is added to the resinsolution which contains 250 parts of 100 percent resin (2a); 534 partsof a 50 percent aqueous solution of ethylenimine is dripped into thissolution at 80 to 85 C. within 4 hours. When all the ethylenimine hasbeen added, the temperature is kept at 80 C. for minutes. The resinsolution obtained has a solids content of 50.2 percent (determined asabove), a density of 1.094 g./cm. and a viscosity of 753 centipoises at25 C. (determined as above).

c. 750 parts of the solution 2b is diluted with an equal amount of waterand then 21.4 parts of epichlorohydrin is dripped in at 70 C. within 90minutes. After the whole has been stirred for another 90 minutes at 70C. the resin solution has a viscosity of 1,100 centipoises at 25 C.(determined as above) at a solids content of 26 percent. The specificviscosity of the product is 0.91 and the. density 1.048 g./cm. (bothdetermined as above). In papermaking the following effects can beachieved in the presence of this resin:

ACCELERATION 0F DEWATERING: (measured as increase in freeness in SR)Pulp: unbleached sulfite cellulose, laboratory grinding in the Riethbeater.

pH 7.3 pH 4.8

1.5% alum Addition (cross-linked resin 100% with reference to absolutelydry cellulose) 0.10 0.15% 0.10 0.15% O-valve 56 63 cross-linked PEI(according to British Pat. No. 1,156,516) 42 31 56 53 Example 2c: 42.535 41 35 EXAMPLE 3 a. 450 parts of water and 495 parts ofdiethylentriamine are placed in a receptacle and 675 parts of adipicacid and 1 13 parts of caprolactam are slowly added at temperatures upto C. Then water is distilled off under nitrogen and the temperature iskept for 2 hours at C., then the bottoms are slowly heated to 150 C.,kept for 3 hours at this temperature and then heated to 170 C. and keptat this temperature until the acid number of the resin at thistemperature until the acid number of the resin has fallen below 10. Whenthe condensation is over, the whole is cooled to to C. and thecondensation product is dissolved in 1,150 parts of water. Thepolyamidoamine solution has a concentration of 51.0 percent. The contentof basic nitrogen is 5.74 percent with reference to 1,004 resin. The 50percent aqueous resin solution has a viscosity of 1,000 centipoises at25 C. (determined as above) and a density of 1.096 g./cm. at 25 C.

b. (a,B, 7) 1,000 parts of a solution of the resin 3a adjusted to asolids content of 50 percent has 85 parts of a 50 percent aqueoussolution of p-toluenesulfonic acid added to it and the whole is heatedto 70 C. At 70 to 80 C., B parts of a 50 percent aqueous ethyleniminesolution is dripped in within A minutes; after all the ethylenimine hasbeen added, the solution is kept for another 3 hours at 80 C. and thencooled to room temperature.

0. (a,,B,'y)vThe solution from (b) is diluted with C parts of water andD parts of epichlorohydrin is added to this solution at roomtemperature; then the whole is heated to 60 C. within 30- minutes andkept at this temperature until there is no further increase in viscositydetectable (period from 2 to 3 hours). The end product has a specificviscosity of E at 15 C.

(determined as above).

Batch A B C D E a 448 1,533 28 0.70 B 240 915 L990 34 0.74 y 400 1,3702,455 39 0.76

In papermaking the following effects can be achieved in the presence ofthe said resin: Acceleration of Dewatering: (measured as increase infreeness in SR) Pulp: newsprint Filler Retention:

(percent ash in paper) v Pulp: 80 percent bleached sulfite cellulose35SR 20 percent china clay Addition: 0.015 percent of crosslinked resin(100 percent) with reference to fiber and filler.

pH 6 pH 4.5

Addition of alum (with reference to fiber and filler) 0.5% 3.5% O value6.4 6.5 cross-linked PEI (according to British Pat. No. 1,156,516) 8.16.5

solution is added to 2,000 parts of the resin solution from Example 3adiluted to a solids content of 50 percent and at 70 to Flocculation:

Characterized by visual comparison of the flocculation and sedimentationrates. The amount added in pans of crosslinked resin per 10 parts offiber suspension having a content CII 3I720 parts of 50 percent aqueousethylenimine sohb 5 of 0.03 percent of absolutely dry fiber in order toproduce the tion is added in the course of 220 minutes. When all the figzfgifgj asthe measure ethylenimine has been added the whole is kept at80 C. for Fb II b] h d I H I I another 2 hours. The resin solutionobtained has a viscosity of 1 mus g z gas 6 w Ce u ground m 1,300centipoises at 25 C. and a solids content of 49.5 per- 1O Stonewareeater cent (both determined as above). I I

c.- 2,270 parts of the resin solution (4b) is diluted with an II" 7 "3 4I m JIIIIII equal amount of water. 43 parts of epichlorohydrin is addedat Adding" omowfinhd Min 25 C. and the mixture is heated to 60 C.; 1hour later the per 10" parts 0.03% suspension of resin solution has aviscosity of 210 centipoises at 25 C. fihmmmacm' cross-linked PEl(determined as above); within 5 hours another 4.2 parts of (accordingmepichlorohydrin is added. The viscosity of the solution thus BritishPat. No. 1,156,516) 1.2 no flocculation rises to 750 centipoises at 25C. The 25 percent solution of II I 4 I 10 sthe cross-linked product 15ad usted to pH 8 with 450 parts of Z T Z Z CIIIIIIIIIIIIIII 85 percentformic acid and EldJUStCd to a solution having 20 (d) 3 15 percent ofactive substance with 943 parts of water. This solution has a density of1.060 g./cm. and a viscosity of 560 centipoises (determined as above).The following effects can be X PL 5 l, par s ofagrafted resin solutionachieved in the presence of this resin in the manufacture of p p eaccording to Example 3 e) is miXed at i h paper: 1,050 parts of waterand 52 parts of methyl acrylate. After Acceleration of Dewatering:(measured as increase in freeness Stirring for 2V2 hours at 60 to 65 C.,the viscosity of the in SR) solution is 700 centipoises at 25 C.(measured as above). The Pulp l: newsprint beaten in an Ultraturraxapparatus; solution has a solids content (measured as above) of 24.8Pulp II: unbleached sulfite cellulose (Rieth beater): percent, a densityof 1,044 g./cm. and a specific viscosity of I II Neutral Neutral mediumpH 5 medium pH 5 Alum (with reference to bone-dry cellulose), percent 1.5, 1. 5 Addition percent (with reference to absolutely dry cellulose)0.10, 0.15 0.10, 0.15 0 10, 0.15 0 10, 0 15 O-volue 48. 4 47 59 58Crosslinked PEI (according to British Patent No. 1,156,516) 27, 25 34,3349 39 43, 311

Filler Retention: (percent ash in the paper) Addition: 0.015 percent ofactive substance with reference to fiber and filler.

pH 6; 0.5% alum pH 5,15% alum O-value 5.3 5.1 cross-linked PEl(according to British Pat.

No. 1,156,516) 5.9 5.2 Example 4c: 6.8 7.]

Comparative Experiments:

For comparison, polyamidoamines which have been crosslinked withepichlorohydrin but have not been reacted with ethylenimine are testedfor their properties in use. They are prepared in the following way:

d. 1,000 parts of a 50 percent aqueous polyamidoamine solution preparedaccording to Example 3(a) is diluted with 1,000 parts ofwater andcross-linked at 60 to 70 C. with 30.6 parts of epichlorohydrin within 20hours; the 25.2 percent solution of the product has a viscosity of 4,500centipoises at 25 C. (determined as above).

e. Cross-linking is carried out analogously to (d) but with only 29.8parts of epichlorohydrin. The 25 percent resin solution obtained has aviscosity of 900 centipoises at 25 C. (determined as above).

Acceleration ofDewatering: (measured as increase in freeness in SR) Testsubstance: unbleached sulfite cellulose; grinding in a Rieth beater:

Neutral pH 4.8; medium 1.5% alum Addition (erosslinkcd resin (100%) withreieronce to absolutely dry cellulose), percent 0. 10,0. 15 0. 10,0.15O-value 54 57. 5 Crosslinked PEI (according to British Patent No.1,156,516) 41,31.5 49, 47 Example 40 43, 31 37. 5, 33 Comparativeexperiment ((1). 48, 42. 5 44. 5, 36. 6 Comparative experiment (0) 4B.5, 46 B, 43 5 1:1 mixture of erossllnkod IEl (British Potent No.1,15(l,l11(1)nm1 )Ulylllllltlnllllllllti(001111311111- ilvu oxtmrltnonl.(11S) 10,31) -17, 45

0.87. The following effects are achieved in the manufacture of paperwith unbleached sulfite cellulose in the presence of this cross-linkedresin:

cellulose) 0.10% 0.15% 0.10% (1.15% O-valuc: 59 56 Example 5c 40 33 3937.5

A product having the same properties is obtained when methyl acrylate isreplaced by the equivalent amount of ethyl acrylate.

EXAMPLE 6 a. 146 parts of adipic acid and 51 parts ofhexamethylenediamine adipate (AH-salt) is added under nitrogen to 108parts of diethylenetriamine and 108 parts of water. The whole is heatedwithin 4 hours (with slow distillation of water) to 150 C. (bottomstemperature) and within another 4 hours to C. The product then has anacid number of 5.0. The melt is cooled and 260 parts of water is addedat 130 C.

The 50 percent aqueous resin solution has a viscosity of 600 centipoises(measured as above) and contains 2.7 percent of basic nitrogen withreference to resin solution.

b. 4.5 parts of p-toluenesulfonic acid is added to 100 parts of a 50percent solution of the polyamidoamine (6a) and at 90 C. 200 parts of 50percent aqueous ethylenimine solution is dripped in within 4 hours.

c. The solution (6b) obtained is diluted to a solids content of 25percent. Epichlorohydrin is dripped in slowly at 70 C.

neutral medium pH 4.8; 1.5% alum Addition (cross'linked resin (100%)with reference to absolutely dry cellulose) 0.10% 0.15% 0.10% 0.15%

Ovalue 56 53 Example 6t: 45 33 45 36.5.

EXAMPLE 7 a. A mixture of 250 parts of water, 525 parts ofdiethylenetriamine, 150 parts of ethylenediamine, 340 parts ofcaprolactam and 1,090 parts of adipic acid is heated to 170 C. withinhours while distilling off water and kept at this temperature until theacid number has fallen below 10; then water is added at 130 C. to dilutethe mixture to a 50 percent resin solution. This has a viscosity of 870centipoises at 25 C. (measured as above) and a content of 1.96 percentof basic nitrogen with reference to 100% resin.

b. 54 parts of p-toluenesulfonic acid is added to 2,000 parts of the 50percent aqueous resin solution (7a). 2,440 parts of 50 percentethylenimine is dripped in within 5 hours at 80 to 90 C. and thesolution is kept at 80 C. for another 3 hours.

c. Epichlorohydrin is dripped into 1,000 parts of the solution (7b)adjusted to 25 percent of solids content and the rise in viscosity iswatched during crosslinking. The viscosity of the solution (measured asabove) rises within 3 hours to 850 centipoises during the slow additionof l 1.1 parts of epichlorohydrin. The solution obtained is adjusted toa solids content of 25 percent and then has a viscosity of 600centipoises and a specific viscosity (measured as above) of 0.89. Thefollowing dewatering and retention values are obtained in the presenceof this product:

Retention (percent of ash in the paper) Substance: 80 percent ofbleached sulfite cellulose 35SR 20 percent ofchina clay Addition: 0.015percent of cross-linked resin (100 percent) with reference to fiber andfiller.

Acceleration of Dewatering: (measured as increase in freeness in SR)Substance: unbleached sulfite cellulose (grinding in Rieth beater) pH4.8; 1.5% alum Addition (cross-1inked resin (100%) with reference toabsolutely dry cellulose) 0.10% 0.15% O-value 59 cross-linked PEI(prepared according to British Pat. No. 1,156,516) 49 47 Example 7c 4338 EXAMPLE 8 a. A 50 percent resin solution is prepared according toExample 2(a). It contains 6.7% of basic nitrogen with reference to the100% product.

b 145 g. of 50 percent sulfuric acid is added to 1,000 parts of theresin solution (a) in the course of 30 minutes. Then 2,000 parts of a 50percent aqueous ethylenimine solution is added at 80 to 90 C. in thecourse of 4% hours and the reaction mixture is kept at 85 C. for anotherhour. The resultant solution of the grafted product is adjusted to asolids content of 45 percent and then has a density of 1.096 g./cm. at25 C. and a viscosity (measured as above) of 368 centipoises at 25 C b244 g. of 50 percent sulfuric acid is added to 1,000 parts of the resinsolution (a) in the course of 30 minutes and the whole is reacted withethylenimine as described in paragraph (b,). The resin solution obtainedis adjusted to a solids content of 45 percent and then has a density of1.087 g./cm. at 25 C. and a viscosity (measured as above) of 306centipoises at 25 C 0 400 parts of the 50 percent solution (b,) isdiluted with 400 parts of water. 1 1.32 parts of epichlorohydrin isadded at 75 to 85 C. in the course of 5 hours and the grafted product iscross-linked. The solution is adjusted to a solids content of 25 percentand then has a viscosity (measured as above) of 1,085 centipoises at 25C. and a density of 1.051 g./cm. at 25 C.

0 12.62 parts of epichlorohydrin is added to 400 parts of the 50 percentsolution (b as described in paragraph (0,). The resin solution obtainedis adjusted to a solids content of 25 percent and then has a viscosity(measured as above) of 1,122 centipoises at 25 C. and a density of 1.046g./cm. at 25 C.

The resin solutions (c and (c are adjusted to pH 8.25 with 85 percentformic acid and diluted to a content of active substance of 20 percent.In papermaking, the following effects are obtained in the presence ofthese resins:

Acceleration of Dewatering: (measured as increase in freeness in SR)Pulp: unbleached sulfite cellulose; laboratory grinding in a Riethbeater.

pH 7.3 pH 4.8; 1.5% alum Addition (erpss-linked resin (100%) withreference to absolutely dry cellulose) 0.10% 0.15% 0.10% 0.15% O-value56 56 Example 2 (c) 44 31 37 33 Example 8 (c,) 46 36 38 32 Example 8 (c45 36 37 32 EXAMPLE 9 a. A 50 percent resin solution is preparedaccording to Example 2(a). 1t contains 6.7 percent of basic nitrogenwith reference to the 100 percent product.

b. 70 parts of 50 percent sulfuric acid is added to the resin solution(a). Then 2,000 parts of a 50 percent aqueous ethylenimine solution isadded uniformly in the course of 4 hours at 85 C. The reaction mixtureis then stirred for 4 hours at 85 C. The solution obtained is adjustedto a solids content of 45 percent and then has a density of 1.079 g./cm.at 25 C. and a viscosity (measured as above) of 388 centipoises at 25 c.200 parts of the 50 percent solution of the grafted product (b) isdiluted with water to a solids content of 25 percent. The dissolvedresin is cross-linked in the course of q hours (total reaction time incross-linking) at 65 to 70 C. by adding n parts of cross-linking agent Xin the course of m hours. The resin solutions obtained are adjusted to asolids content of 25 percent and then have a viscosity (measured asabove) of Y centipoises at 25 C.

n X in q Y (a) 7.05 epichlorohydrin 2.5 3.5 745 (,8) 9.651,3-dichloropropanol-2 3 6 840 5.06 1,4-dichlorobutene-2 2.24.5 975 (6)5.18 adduct of sodium bisulfite to Addition at 70 C, further reaction at80 C.

1n papermaking, the following effects are obtained in the presence ofthese cross-linked resins: Acceleration of Dewatering: (measured asincrease in freeness in SR) Pulp: unbleached sulfite cellulose neutralmedium pH 4.8; 1.5% alum Addition (cross-linked resin (100% withreference to absolutely dry Cellulose) 0.10% 0.15% 0.10% 0.15% O-value57 54 Filler Retention: (percent ash in paper) Pulp: 80 percent ofbleached sulfite cellulose 35SR percent of china clay Addition: 0.03percent of cross-linked with reference to fibers and filler.

resin (100 percent) pH 6 pH 4.8 Addition of alum (with reference tofibers and fillers) 0.5% 1.5% Ovalue 4.5 5 Example 9(c) (or) 12.3 11.2([i) 12.5 11.2 (7) 12.6 11.4

where R denotes an aliphatic alkylene group having from two to sixcarbon atoms with 0.8 to 1.5 moles of a polyalkylenepolyamine of theformula where x denotes an integer from 2 to 6 and n an integer from 1to 3 and up to 0.4 mole of an w-amino-carboxylic acid or its lactamofthe formula wherein R" denotes an aliphatic alkylene group having fromfour to six carbon atoms;

b. reacting the reaction product of step (a) in an aqueous solution orin a solution ofa mixture ofwater and a watersoluble solvent, thesolution having a solids content of from 30 to 90 percent by weight ofthe reaction product of step (a), at a temperature of from 25 to 100 C.with l to 30 moles ofan alkyleneimine (1) of the formula where R and Rdenote a member selected from the group consisting of hydrogen and analkyl group having from one to three carbon atoms, in the presence offrom 0.055 to 1 equivalent of an acid or an alkylating agent (11), themolar amount of (I) and (11) being with reference to one mole of basicnitrogen in the reaction product of step (a); and

c. thereafter reacting the product obtained in step (b) in an aqueoussolution or in a solution of water and a watersoluble organic solvent,the solution having a solids content of from 10 to 40 percent by weight,with about 1 to 20 percent by weight, with reference to the product ofstep (b), of a bifunctional, cross-linking agent at a temperature offrom 40 to 100 C. and cross-linking the product of step (b) to such adegree that a solution containing 25 percent by weight of said producthas a viscosity offrom 300 to 4,000 centipoises (25 C). 2. A process asclaimed in claim 1, which comprises a. reacting 1 mole ofa dibasic acidof the formula HOOC-R-COOH,

where R is an aliphatic alkylene group having from two to four carbonatoms, with 0.9 to 1.2 moles of a polyalkylenepolyamine selected fromthe group consisting of diethylenetriamine, triethylenetetramine,dipropylenetriamine, tripropylenetetramine and tetraethylenepentamine,and up to 0.4 mole of w-aminocaproic acid or caprolactam and b) reactingthe reaction product of step (a) in an aqueous solution having a solidscontent of from 30 to percent by weight in the presence of from 0.05 to1 equivalent of an acid (11) selected from the group consisting ofsulfuric acid, o-and p-toluene-sulfonic acid, phosphoric acid.hydrochloric acid with 2 to 20 moles of ethylenimine (l), the molaramounts of (1) and (11) being with reference to 1 mole of basic nitrogenin the reaction product of step (a) at a temperature from 25 to C., and

c. thereafter reacting the reaction product of step (b) in an aqueoussolution having a solids content of from 15 to 30 percent by weight at atemperature of from 40 to 100 C. with l to 20 percent by weight, withreference to the solids content, of a bifunctional cross-linking agentselected from the group consisting of epichlorohydrin, methyl acrylate,ethyl acrylate, 1,3-dichloropropanol-2, 1,4-dichlorobutane, the additionproduct of sodium hydrogen sulfite to hexamethylene diisocyanate and thereaction product of pentaerythritol, glycerol and epichlorohydrin, whichreaction product has an epoxy equivalent of from 0.5 to 0.8 per 100 g.of reaction product and a chlorine content of from 5 to 10 percent byweight of chlorine; and cross-linking the reaction product of step (b)to such a degree that a solution containing 25 percent by weight of saidcross-linked product has a viscosity of from 500 to 2,000 centipoises(25 C.

3. A process as claimed in claim 1, wherein the reaction product of step(a) comprises 1 mole of adipic acid and 0.9 to 1.2 moles ofdiethylenetriamine,

4. A process as claimed in claim 3, wherein the reaction product 0s step(a) further comprises up to 0.4 mole of caprolactam.

5. A process as claimed in claim 2, wherein the reaction product of step(a) further comprises up to 30 percent by weight of thepolyalkylenepolyamine of a diamine selected from the group consisting ofethylenediamine, propylenediamine and hexamethylenediamine.

6. A process as claimed in claim 3, wherein an aqueous solution of thereaction product of step (a) having a solids content of 50 percent byweight is (b) reaction at a temperature from 40 to 100 C. with 2 to 20moles of ethylenimine (I) in the presence of from 0.05 to 1.0 equivalentof sulfuric acid or toluene-sulfonic acid (II), the molar amount of (I)and (II) being with reference to 1 mole of basic nitrogen in thereaction product of step (a); and

c. thereafter the reaction product of step (b) is further reacted in anaqueous solution, having a solids content of from 15 to 30 percent byweight with 2 to 10 percent by weight, with reference to the solidscontent of the solution, of epichlorohydrin at a temperature of from 40to 100 C., and the reaction product of step (b) is further cross-linkedto such a degree that a solution containing 25 percent by weight of saidcross-linked product of step (b) has a viscosity of from 500 to 2,000centipoises (25 C.).

7. A process as claimed in claim 6 wherein the cross-linking agent isthe reaction product of pentaerythritol, glycerol and epichlorohydrin,which agent has an epoxy equivalent of from 0.5 to 0.8 per 100 g. ofreaction product and a chlorine content offrom to 10 percent by weight.

8. A process for producing paper which comprises adding to an aqueoussuspension of cellulosic fibers for making sheet from about 0.01 toabout 0.3 percent, with reference to the weight of the dry pulp, of awater-soluble cross-linked reaction product obtained by a. reacting 1mole of terephthalic acid or a dicarboxylic acid of the formulaHOOCRCOOH, where R is an aliphatic alkylene group having from two tofour carbon atoms, with 0.9 to 1.2 moles of an aliphatic amine selectedfrom the group consisting of diethylenetriamine, triethylenetetramine,tetraethylenepentamine, dipropylenetriamine, and tripropylenetetramine,

b. thereafter reacting the reaction product of step (a) in an aqueoussolution having a solids content of from 30 to 90 percent by weight at atemperature of from 40 to 100 C. with 2 to 20 moles of ethylenimine (I)in the presence of 0.05 to 1 equivalent of an acid (II) selected fromthe group consisting of sulfuric acid, oand p-toluenesulfonic acid,phosphoric acid and hydrochloric acid, the molar amount of (I) and (Il)being with reference to 1 mole of basic nitrogen in the reaction productof step (a); and thereafter 1 c. reacting the reaction product of step(b) in an aqueous solution having a solids content of from to 30 percentby weight at a temperature of from 40 to 100 C. with 1 to percent byweight, with reference to the solids content, of a bifunctionalcross-linking agent selected from the group consisting ofepichlorohydrin, methyl acrylate, ethyl acrylate,1,3-dichloropropanol-2, 1,4-dichlorobutane, the addition product ofsodium bisulfite to hexamethylene diisocyanate and the reaction productof pentaerythritol, glycerol and epichlorohydrin, which reaction producthas an epoxy equivalent of from 0.5 to 0.8 per g. of reaction productand a chlorine content of from 5 to 10 percent by weight; andcross-linking the reaction product of step (b) to such a degree that asolution containing 25 percent by weight of the said cross-linkedproduct has a viscosity of from 500 to 2.000 centipoises (25 C).

9. A process as claimed in claim 8 wherein the reaction product of step(a) comprises 1 mole of adipic acid and 0.9 to l .2 moles ofdiethylenediamine.

10. A process as claimed in claim 8 wherein the reaction product of step(a) further comprises up to 0.4 mole of caprolactam.

11. A process as claimed in claim 8 wherein the reaction product of step(a) further comprises up to 30 percent by weight of thepolyalkalenepolyamine of a diamine selected from the 7 group consistingof ethylenediamine, propylenediamine and hexamethylenediamine.

12. A process as claimed in claim 8 wherein the water-solublecross-linked reaction product is prepared by reacting the reactionproduct of step (a) in an aqueous solution having a solids content of 50percent by weight at a temperature of from 40 to 100 C. with 2 to 20moles of ethylenimine (l) in the presence of from 0.05 to 1.0 equivalentof sulfuric acid or toluenesulfonic acid (II), the amount of (I) and(II) being with reference to one mole of basic nitrogen in the reactionproduct of step (a); and

c. thereafter reacting the reaction product of step (b) in an aqueoussolution having a solids content of from 15 to 30 percent by weight with2 to 10 by weight, with reference to the solids content of the solution,ofepichlorohydrin at a temperature of from 40 to 100 C. andcross-linking the reaction product of step (b) to such a degree that asolution containing 25 percent by weight of said cross-linked producthas a viscosity of from 500 to 2,000 centipoises 25 C).

13. A process as claimed in claim 8, wherein the reaction product ofstep (b) is cross-linked with a reaction product of pentaerythritol,glycerol and epichlorohydrin, which reaction product has an epoxyequivalent of from 0.5 to 0.8 per 100 g. of the reaction product and achlorine content of from 5 to 10 percent by weight.

14. Paper sheet material produced by the process as claimed in claim 8.

15. Paper sheet material produced by the process as claimed in claim 13.

@2 3 UNITED STATES PATENT OFFICE CERTIFICATE OEF'CORRECTEON Patent No.5, ,57 Dated February 5, 97

mam s Horst Endres et a1 It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

First page, left-hand column, Filed: Mar. 6, 1969 should read [22]Filed: Oct. 6, 1969 First page, right-hand column, fifth line of theabstract, "W-amino-caproic should read w-amino-caproic at the end of theabstract, add This reaction product is added to paper pulp in an amountof 0.01 to 0.3 percent by weight of dry pulp as a drainage aid orflocculating agent.

Column 2, line 70, "gratedon should read grafted-on Column 5, lines 26to 30, "6.4 6.5" should read-- 6.4 6.5

Column 6, lines 56 t 59, "56 55 should read 56 55 Column 10, lines &3and 4 "56 should read 56 5 +4 Bill 44 51 line 75, "2.24.5" should read2. 2 4.5

Column 12, line 71, claim 4, ",os should read of Column 13, line 5,claim 6, "reaction" should read reacted Column 1M, line 22, claim 11,"polyalkalenepolyamine" should read polyalkylenepolyamine Signed andsealed this 2.6th, day of September 1972.

(SEAL) Attest':

EDWARQMFLETCHER ,JR. ROBERT GOTTSCHALK Attestlng Officer Commissioner ofPat nts

2. A process as claimed in claim 1, which comprises a. reacting 1 moleof a dibasic acid of the formula HOOC-R-COOH, where R is an aliphaticalkylene group having from two to four carbon atoms, with 0.9 to 1.2moles of a polyalkylenepolyamine selected from the group consisting ofdiethylenetriamine, triethylenetetramine, dipropylenetriamine,tripropylenetetramine and tetraethylenepentamine, and up to 0.4 mole ofomega -amino-caproic acid or caprolactam and b) reacting the reactionproduct of step (a) in an aqueous solution having a solids content offrom 30 to 90 percent by weight in the presence of from 0.05 to 1equivalent of an acid (II) selected from the group consisting ofsulfuric acid, o-and p-toluene-sulfonic acid, phosphoric acid,hydrochloric acid with 2 to 20 moles of ethylenimine (I), the molaramounts of (I) and (II) being with reference to 1 mole of basic nitrogenin the reaction product of step (a) at a temperature from 25* to 100*C., and c. thereafter reacting the reaction product of step (b) in anaqueous solution having a solids content of from 15 to 30 percent byweight at a temperature of from 40* to 100* C. with 1 to 20 percent byweight, with reference to the solids content, of a bifunctionalcross-linking agent selected from the group consisting ofepichlorohydrin, methyl acrylate, ethyl acrylate,1,3-dichloropropanol-2, 1,4-dichlorobutane, the addition product ofsodium hydrogen sulfite to hexamethylene diisocyanate and the reactionproduct of pentaerythritol, glycerol and epichlorohydrin, which reactionproduct has an epoxy equivalent of from 0.5 to 0.8 per 100 g. ofreaction product and a chlorine content of from 5 to 10 percent byweight of chlorine; and cross-linking the reaction product of step (b)to such a degree that a solution containing 25 percent by weight of saidcross-linked product has a viscosity of from 500 to 2,000 centipoises(25* C.).
 3. A process as claimed in claim 1, wherein the reactionproduct of step (a) comprises 1 mole of adipIc acid and 0.9 to 1.2 molesof diethylenetriamine.
 4. A process as claimed in claim 3, wherein thereaction product os step (a) further comprises up to 0.4 mole ofcaprolactam.
 5. A process as claimed in claim 2, wherein the reactionproduct of step (a) further comprises up to 30 percent by weight of thepolyalkylenepolyamine of a diamine selected from the group consisting ofethylenediamine, propylenediamine and hexamethylenediamine.
 6. A processas claimed in claim 3, wherein an aqueous solution of the reactionproduct of step (a) having a solids content of 50 percent by weight is(b) reaction at a temperature from 40* to 100* C. with 2 to 20 moles ofethylenimine (I) in the presence of from 0.05 to 1.0 equivalent ofsulfuric acid or toluene-sulfonic acid (II), the molar amount of (I) and(II) being with reference to 1 mole of basic nitrogen in the reactionproduct of step (a); and c. thereafter the reaction product of step (b)is further reacted in an aqueous solution, having a solids content offrom 15 to 30 percent by weight with 2 to 10 percent by weight, withreference to the solids content of the solution, of epichlorohydrin at atemperature of from 40* to 100* C., and the reaction product of step (b)is further cross-linked to such a degree that a solution containing 25percent by weight of said cross-linked product of step (b) has aviscosity of from 500 to 2,000 centipoises (25* C.).
 7. A process asclaimed in claim 6 wherein the cross-linking agent is the reactionproduct of pentaerythritol, glycerol and epichlorohydrin, which agenthas an epoxy equivalent of from 0.5 to 0.8 per 100 g. of reactionproduct and a chlorine content of from 5 to 10 percent by weight.
 8. Aprocess for producing paper which comprises adding to an aqueoussuspension of cellulosic fibers for making sheet from about 0.01 toabout 0.3 percent, with reference to the weight of the dry pulp, of awater-soluble cross-linked reaction product obtained by a. reacting 1mole of terephthalic acid or a dicarboxylic acid of the formulaHOOC-R-COOH, where R is an aliphatic alkylene group having from two tofour carbon atoms, with 0.9 to 1.2 moles of an aliphatic amine selectedfrom the group consisting of diethylenetriamine, triethylenetetramine,tetraethylenepentamine, dipropylenetriamine, and tripropylenetetramine,b. thereafter reacting the reaction product of step (a) in an aqueoussolution having a solids content of from 30 to 90 percent by weight at atemperature of from 40 to 100* C. with 2 to 20 moles of ethylenimine (I)in the presence of 0.05 to 1 equivalent of an acid (II) selected fromthe group consisting of sulfuric acid, o- and p-toluenesulfonic acid,phosphoric acid and hydrochloric acid, the molar amount of (I) and (II)being with reference to 1 mole of basic nitrogen in the reaction productof step (a); and thereafter c. reacting the reaction product of step (b)in an aqueous solution having a solids content of from 15 to 30 percentby weight at a temperature of from 40* to 100* C. with 1 to 20 percentby weight, with reference to the solids content, of a bifunctionalcross-linking agent selected from the group consisting ofepichlorohydrin, methyl acrylate, ethyl acrylate,1,3-dichloropropanol-2, 1,4-dichlorobutane, the addition product ofsodium bisulfite to hexamethylene diisocyanate and the reaction productof pentaerythritol, glycerol and epichlorohydrin, which reaction producthas an epoxy equivalent of from 0.5 to 0.8 per 100 g. of reactionproduct and a chlorine content of from 5 to 10 percent by weight; andcross-linking the reaction product of step (b) to sucH a degree that asolution containing 25 percent by weight of the said cross-linkedproduct has a viscosity of from 500 to 2,000 centipoises (25* C).
 9. Aprocess as claimed in claim 8 wherein the reaction product of step (a)comprises 1 mole of adipic acid and 0.9 to 1.2 moles ofdiethylenediamine.
 10. A process as claimed in claim 8 wherein thereaction product of step (a) further comprises up to 0.4 mole ofcaprolactam.
 11. A process as claimed in claim 8 wherein the reactionproduct of step (a) further comprises up to 30 percent by weight of thepolyalkalenepolyamine of a diamine selected from the group consisting ofethylenediamine, propylenediamine and hexamethylenediamine.
 12. Aprocess as claimed in claim 8 wherein the water-soluble cross-linkedreaction product is prepared by reacting the reaction product of step(a) in an aqueous solution having a solids content of 50 percent byweight at a temperature of from 40* to 100* C. with 2 to 20 moles ofethylenimine (I) in the presence of from 0.05 to 1.0 equivalent ofsulfuric acid or toluenesulfonic acid (II), the amount of (I) and (II)being with reference to one mole of basic nitrogen in the reactionproduct of step (a); and c. thereafter reacting the reaction product ofstep (b) in an aqueous solution having a solids content of from 15 to 30percent by weight with 2 to 10 by weight, with reference to the solidscontent of the solution, of epichlorohydrin at a temperature of from 40*to 100* C. and cross-linking the reaction product of step (b) to such adegree that a solution containing 25 percent by weight of saidcross-linked product has a viscosity of from 500 to 2,000 centipoises(25* C).
 13. A process as claimed in claim 8, wherein the reactionproduct of step (b) is cross-linked with a reaction product ofpentaerythritol, glycerol and epichlorohydrin, which reaction producthas an epoxy equivalent of from 0.5 to 0.8 per 100 g. of the reactionproduct and a chlorine content of from 5 to 10 percent by weight. 14.Paper sheet material produced by the process as claimed in claim
 8. 15.Paper sheet material produced by the process as claimed in claim 13.